Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this disclosure and are not admitted to be prior art by inclusion in this section.
RI is the key physical interface of radio base station between an REC and an RE. The Common Public Radio Interface (CPRI) is the most successful industry cooperation defined publicly available specification for the Radio Interface (RI). A specification of the CPRI is given in Reference [1] (“Communication Public Radion Interface (CPRI); Interface Specification”, CPRI Specification V5.0, Sep. 21, 2011) which is incorporated herein by reference. User plane data (IQ), control and management plane (C&M) data are transferred over this interface. With the technology development and network evolution, there are different RECs and REs that have different processing and transmission capabilities in the current radio access network. As for the processing and transmission capabilities of an REC and an RE, it can be quantitized as the amount of minimal processing and transmission units that can be processed by an REC or an RE. In the CPRI standard and other standards, such as OBSAI (Open Base Station Architecture Initiative) standard, the minimal processing and transmission unit is denoted as an Antenna-Carrier (AxC). For simplicity, the AxC amount is used in this disclosure to demonstrate the processing and transmission capabilities of an REC or an RE.
Also there are different RECs and REs that support different telecommunication standards, such as Global System for Mobile communication (GSM), Time-Division-Synchronous Code Division Multiple Access (TD-SCDMA), Wideband Code Division Multiple Access (WCDMA), Long Term Evolution (LTE) and etc.
FIG. 1 shows a network topology among RECs and REs in a network. As shown, in the radio network topology, RECs and REs are directly connected to each other even if their processing and transmission capabilities are not matched. In FIG. 1, RECs 1-4 are connected to REs 1-4, respectively, although RECs 1-4 have more processing and transmission capabilities than the connected REs 1-4. 2 AxCs of RECs 1-3 and 6 AxCs of REC 4 are not utilized with the network topology and thus part of the baseband processing and transmission capability of the network is wasted. In the case, the connection of an REC and an RE can only utilize the limited processing and transmission capabilities of the REC and the RE.
For example, when an REC with a processing and transmission capability of 8 AxCs connects to an RE with a processing and transmission capability of 6 AxCs, the REC and the RE together can only have a processing and transmission capability of 6 AxCs and the REC should waste a quarter of its processing and transmission capability. When an REC with a processing and transmission capability of 4 AxCs connects to an RE with a processing and transmission capability of 6 AxCs, the REC and the RE together can only have a processing and transmission capability of 4 AxCs and the RE should waste one third of its processing and transmission capability. Therefore, when an REC connects to an RE with different processing and transmission capabilities, the REC and the RE together can only have limited processing and transmission capabilities used. Thus, one of them cannot work with its highest processing and transmission capability and it will result in the waste of cost and efficiency.
Also, considering traditional User Equipments (UEs) will continue to exist, 2G/3G/4G networks will co-exist for a long time in order to meet the compatibility requirement from customers. Most operators occupy 2 to 3 different telecommunication standards. For example, CHINA mobile holds GSM, TD-SCDMA and TDD-LTE. An RE can only connect to an REC with the same telecommunication standard. For a cascading scenario, an RE can only be cascaded to another RE that supports the same telecommunication standard. For mix-mode cascading requirement from operators, a traditional REC can only support a single telecommunication standard and REs of different telecommunication standards will locate on the same cascading chain. It is impossible to communicate between several single-mode RECs and one mix-mode cascading chain.
Carrier Aggregation (CA) is one of the most distinct features of 4G systems including LTE-Advanced, which is being standardized in 3GPP as part of LTE Release 10. This feature allows scalable expansion of effective bandwidth delivered to a user terminal through concurrent utilization of radio resources across multiple carriers. These carriers may be of different bandwidths, and may be in the same or different bands to provide maximum flexibility in utilizing the scarce radio spectrum available to operators. If the carrier aggregation is implemented on the REC level, only REs that connect to the same REC can be used to implement carrier aggregation, and thus the benefit of carrier aggregation is not used to the most extent.